PARIS — A Sea Launch Zenit 3SL rocket successfully placed Italy’s Sicral 1B military telecommunications satellite into geostationary transfer orbit April 20 in the first of what is likely to be just two launches from the oceangoing Sea Launch platform this year as the Long Beach, Calif.-based company works to resolve rocket-component supply issues.

The 3,038-kilogram Sicral 1B, built by Thales Alenia Space of France and Italy, will operate at 11.8 degrees east longitude. It follows the Sicral 1 satellite, which was launched in 2001 and is located at 16.2 degrees east. Thales Alenia Space officials expect that a long-delayed contract for the Sicral 2 satellite, with payloads for the French and Italian defense ministries, will be signed in the coming weeks.

Sicral 1B carries one EHF-frequency transponder, three transponders in the UHF band and five SHF-band transponders. Thales Alenia Space officials said it is designed to operate for 13 years.

In addition to the Italian Defense Ministry, Sicral 1B’s users will include the NATO alliance as part of a three-nation satellite-telecommunications contract including the Skynet 5 satellites owned and operated by Astrium Services, and the Syracuse satellites operated by the French Defense Ministry.

About one-third of the Sicral 1B payload has been reserved for use by Telespazio of Rome in return for Telespazio’s sharing of the cost of Sicral 1B’s development and launch.

Telespazio officials have said they are willing to enter into a similar arrangement for Sicral 2, which they still hope will be ready in time for a 2012 launch.

Italian authorities had selected Sea Launch over Europe’s Arianespace consortium for the launch in the hope that, as the sole payload aboard Sea Launch, Sicral 1B could be placed close enough to its final operating position to save fuel and thus extend its in-orbit service life. Sicral 1B managers said an Ariane 5 launch, with Sicral 1B as one of two passengers, would have placed the satellite into a less-favorable parking orbit from a fuel-saving point of view.

Sea Launch Chief Executive Kjell Karlsen said after the launch that Sicral 1B had been placed into a position very close to its target, with an apogee of 35,671 kilometers — just 5.4 kilometers higher than what had been targeted. The perigee, at 8,606.4 kilometers, was just 400 meters off target.

Thales Alenia Space officials said Sicral 1B is designed to operate for 13 years.

The satellite uses an old design, the Italsat 3000, with relatively small fuel tanks. Officials could not be reached for comment on whether the launch-injection coordinates would enable them to operate Sicral 1B for a longer period.

Peter B. de Selding was the Paris bureau chief for SpaceNews.